PRESS ROOT TO CONTINUE: DETECTING OSX AND WINDOWS BOOTKITS WITH RDFU

Transcription

1 Mario Vuksan & Tomislav PericinBlackHat USA 2013, Las Vegas PRESS ROOT TO CONTINUE: DETECTING OSX AND WINDOWS BOOTKITS WITH RDFU

2 Agenda Our motivation Who are we Introduction to Unified extensible framework interface (UEFI) Previous UEFI bootkit research Rootkit detection framework RDFU Framework design VMWare implementation demo MacOSX bootkitdemo

3 Our motivation UEFI is very popular Windows + Android + MacOS+ Full-stack: UEFI is a mini-os Memory and file manipulation, full network stack Graphics APIs, device management Remote boot Attacker s paradise No tools for analysis, low visibility, even no AV, Some good news though UEFI SecureBoot(Surface RT, Android)

4 Who are we ReversingLabs Founded by Mario Vuksan and Tomislav Pericinin 2009 Focusing on Deep binary analysis of PE/ELF/Mach-O/DEX and firmware System reputation and anomaly detections Black Hat presentations and open source projects TitanEngine: PE reconstruction library (2009) NyxEngine: Archive format stego detection tool (2010) TitanMist: Unpacking (2010) Unofficial guide to PE malformations (2011) FDF: disinfection framework (2012) RDFU: UEFI rootkit detection framework (2013)

5 Thanks John Heasman, Black Hat 2007 Snare, Assurance, Black Hat 2012 Dan Griffin, Defcon 2012 Sebastien Kaczmarek, HITB Amsterdam 2013 DARPA CFT

6 UEFI unified extensible firmware interface

7 Booting with BIOS BIOS MBR REAL MODE (16 bit) NTLDR NTOSKRNL.EXE KERNEL HAL SMS USERLAND WIN32 Distribution Statement A (Approved for Public Release, Distribution Unlimited)

8 UEFI? UEFI: Unified extensible firmware interface Originally developed by Intel, Intel boot initiative Community effort to modernize PC booting process Currently ships as a boot option alongside legacy BIOS Aims to be the only booting interface in the future Used in all Intel Macs and other PC motherboards Managed by Unified Extensible Firmware Interface (UEFI) Forum

9 Booting with EFI UEFI UEFI bootloader \EFI\Microsoft\Boot\bootmgfw.efi PROTECTED MODE winload.efi NTOSKRNL.EXE KERNEL HAL SMS USERLAND WIN32 Distribution Statement A (Approved for Public Release, Distribution Unlimited)

10 UEFI Conceptual overview Operating system EFI Operating system loader Other interfaces (ACPI, SMBIOS ) EFI Boot services Platform hardware EFI runtime services EFI partition

11 EFI boot sequence EFI Driver EFI Application EFI Boot code OS Loader Platform init EFI image load EFI OS loader load Boot service terminates Standard firmware initialization Drivers and applications loaded Boot from ordered EFIOS list Operations handed off to OS Boot Manager EFI images

12 UEFI images UEFI images: Typically PE32/PE32+ (basic format feature subset) Standard also predicts that other formats can be defined by anyone implementing the specification, e.g. TE defined by Intel and used by Apple

13 UEFI images UEFI drivers: Boot service driver Terminated once ExitBootServices() is called Runtime service driver UEFI applications: EFI application Normal EFI applications must execute in pre-boot environment OS loader application Special UEFI application that can take control of the system by calling ExitBootServices()

14 UEFI Boot services UEFI boot services: Consists of functions that are available before ExitBootServices() is called These functions can be categorized as global, handle based and dynamically created protocols Global System services available on all platforms Event, Timer and Task Priority services Memory allocation services Protocol handler services Image services Miscellaneous services Handle based Specific functionally not available everywhere

15 UEFI Runtime services UEFI runtime services: Consists of functions that are available before and after ExitBootServices() is called These functions can be categorized as global, handle based and dynamically created protocols Global System services available on all platforms Runtime rules and restrictions Variable services Time services Virtual memory services Miscellaneous services Handle based Specific functionally not available everywhere

16 EDK2 EFI development kit TianoCore Intel s reference implementation Enables writing EFI applications and drivers in C Has its own stdlibcimplementation that covers a part of the standard library Has a set of packages for shell, crypto, emulation and more Has a set of applications built with stdlibc implementation For example: Python 2.7 Has a build system which uses popular compilers (VS, GCC and XCode) Supported CPUs: IA64, x86-64 and ARM

17 EDK2 HelloWorld.c /*** Print a welcoming message. Establishes the main structure of the 0 The application exited Other An error occurred. ***/ INTN EFIAPI ShellAppMain( IN UINTN Argc, IN CHAR16 **Argv ) { Print(L"Hellothere fellow Programmer.\n"); Print(L"Welcome to the world of EDK II.\n"); return(0); }

18 UEFI - HelloWorld.c /*** Print a welcoming message. Establishes the main structure of the 0 The application exited Other An error occurred. ***/ INTN EFIAPI UEFIAppMain( IN EFI_HANDLE ImageHandle, IN EFI_SYSTEM_TABLE *SystemTable/** Boot and Runtime services **/ ) { Print(L"Hellothere fellow Programmer.\n"); return(0); }

19 Bootkits attacking unified extensible firmware interface

20 Previous work 07 Hacking extensible firmware interface John Heasman, NGS Consulting Presented at BlackHat 2007, USA Research Modifying NVRAM variables Code injection attacks Shimming boot services Abusing system management mode

21 Previous work 12 Hacking extensible firmware interface Snare, Assurance Presented at BlackHat 2012, USA Research Patching MacOS X kernel Evil maid attack

22 Previous work 13 Dreamboot Windows 8 x64 bootkit Sébastien Kaczmarek, QuarksLab Presented at HackInTheBox 2013, Amsterdam Modus operandi Bypasses kernel protections (NX and Patch guard) Bypasses local authentication Elevates process privileges

23 Dreamboot UEFI UEFI bootloader \EFI\Microsoft\Boot\bootmgfw.efi winload.efi NTOSKRNL.EXE HAL HOOK! HOOK! HOOK! KERNEL CALLBACK SMS USERLAND WIN32 Distribution Statement A (Approved for Public Release, Distribution Unlimited) CALLBACK

24 RDFU rootkit detection framework for uefi

25 What is RDFU? Set of EFI applications and drivers that enable: Listing all EFI drivers loaded into memory Probing entire memory range, scanning for executable Monitoring newly loaded drivers until operating system starts Listing and scanning EFI BOOT SERVICES and EFI RUNTIME SERVICES for modified function pointers Continually monitoring EFI BOOT SERVICES and EFI RUNTIME SERVICES while operating system is being loaded Displaying memory map and dumping all suitable regions Listing and monitoring EVENT callbacks that can be used by rootkits/malware Working in a standalone mode without the EFI shell

26 What does RDFU support? Supported UEFI implementations: UEFI 2.x specification for 32-bit and 64-bit Implementations UEFI 1.x specification MacOS UEFI implementation VirtualBox VMWare Not supported UEFI implementations: UEFI ARM implementation (only on Surface RT, has secure boot enabled)

27 How does RDFU work? DXE driver loaded via UEFI shell DXE driver loaded from USB thumb drive Scanner application run from UEFI shell Logging and dumping is done to the mounted hard drive or the USB thumb drive

28 VMWARE

29 VMWARE

30 VMWARE

31 VMWARE

32 VMWARE

33 DEMO rootkit detection framework for uefi

34 MAC OS 10.7.x bootkit first MacOS X bootkit example

35 Bootkit goals Create hidden folders Hiding (with un-hiding) processes Execute shell with root privileges Retrieve FileVault password

36 Running the MacOS bootkit Mac OS X 10.7.x -Lion

37 Running the MacOS bootkit Boot the OS from an USB thumb drive

38 VMWare / MacOS bootkit MacOScan also be run in VMWare if you don t have a MacBook Pro handy Running MacOSunder VMWare requires an unofficial patch wink wink nudge nudge Once patched we need to change the VMX file firmware = "efi" After that MacOScan be installed with EFI 1.10

39 Bootkit workflow UEFI EFI\boot\bootx64.efi BS->CreateEvent EVT_SIGNAL_VIRTUAL_ADDRESS_CHANGE SystemTable->ConIn->ReadKeyStroke BS->OpenProtocol LoadedImage->Unload Register event callback HOOK! Fail safe Load Mac OS X

40 Bootkit workflow Load Mac OS X Enumerate drives \System\Library\CoreServices\boot.efi User choice on multiple OS X instances found BS->LoadImage BS->StartImage

41 Bootkit workflow SIGNAL EVT_SIGNAL_VIRTUAL_ADDRESS_CHANGE EVENT SetVirtualAddressMap() Locate syscall table Hook syscalls: setuid, getdirentries, getdirentriesattr& sysctl HOOK!

42 Getting ROOT /*** executes shell with root rights ***/ #define HIDDEN_UID 1911 intmain( void ) { setuid(hidden_uid); system("/bin/sh"); }

43 Hiding processes /*** sends the pidto the rootkit that should be hidden ***/ int main(int argc, char *argv[]) { pid_tpid= atoi(argv[1]); printf("adding pid%d (%08x) hide list\n", pid, pid); int name[] = { CTL_ADD_PID, pid, KERN_PROC_ALL, 0 }; err = sysctl((int*)name, (sizeof(name) / sizeof(*name)) -1, NULL, &length, NULL, 0); } printf("all done, sysctl returned 0x%08x\n", err); return EXIT_SUCCESS;

44 DEMO MacOS X bootkit

45 QA Thanks!